Olfactory receptors (ORs) represent nearly 2% of the mouse genome, reflecting something over 1200 individual genes. This remarkable number represents both an experimental opportunity and a technical challenge. Comparative studies among such a large number of genes expressed in a single tissue can offer insights in questions ranging from receptor-ligand structure-function relations to stimulus coding strategies to regulation of gene expression. However the technical demands of working with a family of over 1000 genes are beyond most standard practices of molecular biology and physiology. The advent of whole genome sequencing and high density microarray gene expression assays are a viable solution to these obstacles, and can provide important front end data that can be pursued further by standard, low throughput techniques. Additionally these high throughput techniques can themselves often produce informative data and new insights. Here we propose to extend our bioinformatics based data mining efforts into dynamic functional studies with a new custom-designed high density microarray that will allow us to monitor expression levels of all olfactory receptor (OR) genes simultaneously. This will allow us to extend the bioinformatics work on the whole genome to an appreciation of dynamic gene expression and regulation.